The invention pertains to cargo handling ramps suitable for loading and unloading various kinds of cargo between ground level and an elevated cargo bay of a transport, such as that of an aircraft.
As disclosed in U.S. application Ser. No. 673,917, filed on Apr. 5, 1976, now U.S. Pat. No. 4,039,163, issued Aug. 2, 1977, by Thomas H. Shorey for AIRCRAFT CARGO RAMP, it is many times necessary to load and unload air transported cargo between a cargo bay of the aircraft and ground level, without the assistance of special, ground-based cargo-handling equipment of the type available at larger air terminals. For example, emergency or temporary airstrips may not be equipped with such specialized ground-based equipment. To fulfill this need, cargo loading/unloading ramps have been developed, wherein such ramps are carried on board the aircraft, within the cargo bay and are deployed prior to loading or unloading so as to extend at an incline between ground level and the threshold of the cargo bay opening. The configuration of ramps of this type is such that rolling cargo, i.e., wheeled and endless belt driven vehicles, can be moved up and down the ramp and thus quickly loaded and unloaded.
In the rolling-cargo ramp disclosed in the above-mentioned application, the ramp is fitted with retractable roller and pallet guide assemblies for converting ramp treadways into inclined roller conveyers for loading and unloading palletized cargo. In this manner, the ramp structure provides the capability of handling a variety of cargo types, in particular a mix of both rolling and palletized cargo.
While the conversion of the treadways to roller conveyors has been found satisfactory for handling small pallets, boxes and the like, the loading and unloading operations are slow and tedious, especially where boxes or small pallets of cargo must be taken from a stack and loaded in a single file fashion on the treadway conveyors, and thereafter removed and individually restacked. Also, to load the cargo, each of the boxes and small pallets must be either manually pushed up the ramp or pulled by a winch, the latter requiring means for somehow attaching the winch cable to the individual boxes and pallets. During unloading, fragile cargo must be lowered slowly or caught as it is slid by gravity down the ramp conveyors.
Similar difficulty is encountered in attempting to load and unload palletized cargo of the type that cannot be unpackaged and moved box by box. For example, heavy machinery is often transported by strapping it to large pallets which are ideally transported and handled as a palletized unit. Such palletize equipment may be too large and heavy to be readily placed on the roller conveyors and lowered or raised along the inclined ramp.
Another disadvantage of the inclined roller conveyors is that the cargo must be tilted to match the incline of the ramp each time it is moved onto the ramp, either from the cargo bay of the aircraft, or from the flat bed of a truck. For small and lightweight cargo this is usually not difficult, however, for large and heavy items, the tilting and relevelling of the cargo each time it is moved on and off the ramp, requires additional time and involves added risk to the safety of the cargo and to the cargo handling crew.
Accordingly, it is an object of the invention to provide an improved, rolling-cargo ramp apparatus of the type that is convertible to a configuration for handling palletized cargo, and which when in the latter configuration is capable of faster, more efficient and safer handling of palletized cargo.
Another object of the invention is to provide such a convertible ramp appparatus which in its pallet handling configuration is capable of loading and unloading relatively large, bulky and/or heavy palletized cargo, such as stacks of boxes carried on a single, large pallet, and heavy machinery or the like strapped to a large pallet.
A further object of the invention is to provide such a convertible ramp apparatus, which in its pallet handling configuration permits the palletized cargo to remain level while being loaded and unloaded. A related object is to provide such a convertible ramp apparatus in which the palletized cargo can be transferred to the pallet handling ramp apparatus from the bed of a truck transport, or from the floor of an aircraft cargo bay while continuously supporting the palletized cargo in a level orientation.
Additionally, it is an object of the invention to provide a convertible ramp apparatus for loading and unloading a mix of rolling and palletized cargo to and from an aircraft cargo bay which is capable of handling a wide variety of pallet sizes, including relatively large pallets, and is capable of accommodating relatively heavy palletized cargo such as large machinery, and which is of a lightweight construction and is collapsible into a relatively small compact assembly suitable for being carried on board the aircraft for use in handling cargo at temporary and emergency airfields where specialized, groundbased cargo handling equipment is unavailable.
It is also an object of the invention to provide such a convertible ramp apparatus that is rugged, reliable, lightweight, adaptable to a wide range of pallet sizes, and is quickly and easily extended into an operative position for loading and unloading and is similarly returned to its stowed position within the cargo bay for flight.